Switching mechanism



Feb. 5, 1952 L. R. EIMERMANN SWITCHING MECHANISM Filed Aug. 3. 1948 2 Sl-IEETS-SHEET 1 INVENTOR. LL90 R. EIMERMANN m2. new

ATTORNEYS Feb. 5, 1952 L. R. EIMERMANN 2,534,532

swrr'cams MECHANISM Filed Aug. 3. 1949 2 SHEETS-SHEET 2 INSULATION M INVENTOR.

L L OYD R. ElMERMANN mam ATTORN EY 5 Patented Feb. 5, 1952 UNITED STATES PATENT OFFICE- SWITCHING MECHANISM Lloyd R. Eimermann, Milwaukee, Wis., assignmto Perfex Corporation, Milwaukee, Wis, a corporation of Wisconsin Application August 3, 1949, Serial No. 108.240

Claims. 1

This invention relates to condition responsive controllers and in particular to pressure respon sive switches which operate with a snap action when the pressure to which the switch responds reaches the control value.

In condition responsive switches of the type under consideration it is customary to make provision for snap movement of the contact carrying apparatus so that, as the condition approaches the control value in small incremental changes, the contacts will remain in their orig inal position until the control value of the condition is reached, and will then snap to their new position, thereby minimizing arcing at the switch contacts as they open and close. One method of securing such snap movement involves use of an over-center spring connection between a contact carrying beam and an actuated beamv A diniculty encountered in this construction is that as the actuated beam moves in contact-opening direction and approaches the dead-center position for the over-center spring, a zone of vanishing contact pressure is traversed within which the contact pressure is reduced and eventually reaches zero causing arcing and consequent deterioration of the contacts.

The principal object of the present invention is to provide a switch mechanism wherein the contact pressure remains constant until the contacts are separated. A further object of the present invention is to provide a switch mechanism wherein the closing of the contacts is. accomplished by an uninterrupted, rapid motion of the contact carrying beam. An additional object of the present invention is to provide a condition responsive switch having safety shut-down means wherein the range setting, difierential setting, and the condition value at which the safety shut-down means operates are all readily adjustable.

Other objects and advantages will become apparent upon examination of the drawings and accompanying description in which:

Fig. 1 represents a side view of the switching mechanism, in schematic form to better illustrate the relation of parts, and showing the mechanism in normal closed contact position.

Fig. 2 is a view similar to Fig. 1 but illustrating the mechanism in normal open contact position.

Fig. 3 is a view similar to Fig. 2 but illustrating the mechanism in open contact position with the parts in a different relationship than that shown in Fig. 2.

Fig. 4 is an enlarged, detail view of aportion of the mechanism. I v

Referring now to Figs. 1, .2, and 3 it will be noted that the mechanism is enclosed in a rec,- tangular boxlike casing having a. base plate 10. a back plate II, a top plate l2, and a 'front plate l3, of which a portion only is shown. A l in l5 extends through the, casing and is journaled in front plate l3 and back plate ll.

Pivotally mounted on pin l5 by means of two upturned ears 18 (only one. of whichis shown) and extending lengthwise oi the casing is a main operating lever or actuating beam l5.- The plvotal mounting of beam i6 is at a point intermediate its ends, one end of beam 16 having an up turned portion ll for connection with a switch operating mechanism which will presently be described in detail. Also, pivotally mount d. on pin is is an actuated beam, 2.0. having two down: wardly extending ears, 22 (only one of which is shown) throu h which pin. 15 e tends.

A diflerential beam 25 is also pivotally mounted on pin l5 by means of two upwardly extending ears 21. Beam 25 is generally coextensive with beams 20 and I6. Beams, 20 and 1,6 are held in spaced relationship by means of a pacer 29 mounted on. beam 20; extending through an opening in beam 25 and engagin beam 16. Beam I6 is resiliently held in engagement with spacer 29 by means of a strain relief spring 32 which is a compression spr n having one end bearing a ainst a sprin r ai er and its other end bearing against the upper side. or beam 20,. The retainer 33 is secured toe pin .3. w ch xtends throu h the center of spring 32 and loosely through openings in beams 20, 25 and It. A member 35 and pin 34 form an inverted T-shaped assembly with the member 35 bearing against the underside of beam 15- From the f r oing it wi l be apparen that b ams 16 and 20 are normally held in a spaced relation by ns of sp c r Z and spring 3 but may be moved apart, such movement resulting in fur.- ther compression of spring 32.

Rigidly secured to base plate ID. by any suitable means, is a conv ntional pressure or other condition responsive assembly comprising a case ingv 3B, enclosing an expansible bellows, a

threaded nipple 31, the central bore of which serves as a path for the introduction of an expansible fluid into operative relation with the bellows, and a thrust pin 38 which is moved upwardly or downwardly upon movement of the bellows assembly u der the influence of a 0 1- dition change, as is well known in the art, It will be understood that a capillary tube and bulb filled with a temperature responsive fluid may be attached to the threaded nipple 31. or a tube introducing the pressure into the condition re sponsive assembly of any hydraulic system, the pressure of which is to be controlled, might alternatively be attached to nipple 31, so that the condition responsive assembly may be made to respond either to pressure or temperatu e variations. Q e

Thrust pin 38 engages the underside of beam 28 so that upward movement of pin 38 results in counterclockwise rotation of beam 20 about its pivot l5. Such movement is opposed by arange spring 48, a compression spring, which bears against the top side of beam 20-and against a spring retainer 4| which is threaded upon an adjusting screw 42. The screw 42 has its head 43 overlying the top plate l2, the shankportion of screw 42 extending loosely through an opening in plate l2. It will be apparent that adjustment of screw 42 and consequent movement of retainer 4!, in a vertical plate varies the compressive stress within spring 48 and thereby the force exerted by spring 48 inopposition to upward movement of thrust pin 38.

A pin at, having a head member 45, similar to member 35", extends loosely through openings in beams 25 and 28 and is secured to one end of a'differential' spring 46. The spring 46 is a tension spring and has its other end retained on a stud. 48 by means of a flange 49 formed integrally with the stud 48. Stud 48 is threaded to receive a differential adjusting screw 58 which extends loosely through an opening in plate 12, its head 4'! bearing against plate 12. It will be apparent from the foregoing that adjustment of screw 58 and consequent movement of stud 48 in a'vertical plane varies the tension of spring 48 and'therebythe force'exerted by spring 46 in the direction for'moving beam 25 counterclockwise about its pivot [5, as viewed in Figs. 1, 2 and 3. I

' A bracket 52 is secured to the base plate ID by any suitable means and has an inwardly extending portion 53 through which is threaded a calibration screw-54. Screw 54 serves as a stop, limiting the counterclockwise rotational movement ofbeam 25. Beam 28 has an opening 58 therein through which screw 54 freely extends. A tongue 57, formed on the end of beam 28, extends'freely through a slot 58 in the upright portion of bracket 52. The slot 58 serves to limit the rotational movement of the beam 20.

' The upturned end I! of the beam I6 has attached thereto one end of a tension spring 68. The other end of spring 88 is fastened to the central portion of anoperating lever 6|. Two identical members 64 (only one of Which is shown in the figures) are rigidly secured to the base plate ID and each has a notch 85 near its upper end for receiving the sharpened end of lever 8| thereby forming a-pivotal, knife-edge bearing for the lever 8|. It will be understood that the upturned portion ll of the beam I6 extends between the two members 54, and that the lever 6| has a central, cut-out portion for accommodating the body of spring 88 so that the ends of spring 68 .are substantially. in alignment.

A latch member 61, essentiall channel-shaped in cross-section, is mounted for movement about pin I by means of cars 88 (only one of which is shown) through which pin loosely extends, As may best be seen in Fig. 4, member 61' is biased to move in a clockwise direction about pin 15 by means of a coiled spring 18. Spring 18 has one of its ends fastened to member 6'! and its other end bearing against the end of beam 25. --The limit for counterclockwise movement of member 81 about pin I5 is established by calibrating screw H which is threaded into an opening in an extending tab I2 struck from back plate II.

The switching mechanism 14 as shown in Figs. 1, 2 and 3 includes a switch plate 15, made of any suitable insulating material. Fastened to the plate 15 are two terminal brackets 16 and 11 formed of highly conductive metal. Bracket 15 has an ear 18 extending therefrom to which is secured, by any suitable means, one end of a resilient strip 80. The other end of strip is secured by any suitable means to a switch arm ormember 8|. It will be understood that the resilient strip 80, which interconnects the fixed car 18 and switch arm 8 l serves as a spring hinge for the arm 8|, deforming, as shown in Fig. 2, upon movement of the free end of arm 8|. Attached to the free end of arm 8| by any suitable means is an extension 82, formed of insulating material. The extension 82 extends beyond the switch plate 15 and has at its outer end an car 84 and a depending member 85, having a notched portion 86. The car 84 is adapted to be engaged by the free end of the operating lever 6!, and the notched portion 86 is adapted to receive one edge of the latch member 81, as will subsequently be pointed out in the description of operation of the mechanism. Extending from switch arm 8| is a mounting for a movable contact 88. A compression spring 89 is anchored on a tab 98 extending from the switch plate 15 and exerts a force upon switch arm 8| tending to rotate arm BI (and consequently extension 82) clockwise on its spring hinge 80. The limit of clockwise movement of arm BI is established by the fixed contact 9| which is mounted on an extending portion of the bracket 11. A boss 93, extending outward- 1y from the switch plate 15, houses a permanent magnet 92 which serves as ablow-out magnet in extinguishing the are formed upon opening and closin of the contacts 88 and 9 I.

Mounted on the base plate I8 is a second condition responsive assembly comprising a casing 84, similar to casing 36, enclosing a bellows assembly and a threaded nipple 95, the central bore of which serves as a path for the introduction of a condition responsive fluid into operative relation with the bellows. A thrust pin 91 extends through an opening in the base plate l8 and is adapted to move upwardly or downwardly upon movement of the bellows assembly under the influence of a condition change. Prolonged upward movement of the pin 9! will result in its engagement with, and consequent rotation of beam l8 about its pivotal mounting l5, as shown in Fig. 3.

The mechanism described may be used to control a mechanical refrigeration system. In such an application the nipple 31 may be connected by a suitable conduit to the low pressure line of the refrigeration system, the nipple 95 may be connected to the high side of the compressor, and the contacts 88 and 81 may be connected in series with the compressor motor, such connections being well known in the art.

In operation, if the pressure in the low pressure line of the refrigeration system is above a predetermined value the pin 38 will be in the position shown in Fig. 1. In assuming this position, pin 38 will have moved beam 20, against the force of spring 40, toward its limit of counterclockwise movement. Through spring 82, pin 84, and spacer 29, actuating beam IE will also have been moved counterclockwise an equal amount.

Spring 60 will thereby have been moved below the plane of lever 6|, and, consequently, lever BI and member 61 will have been moved to the position shown in Fig. 1. Contacts 88 and 9| will be closed because of the biasing force exerted by spring 89 on the switch arm 8|. With contacts 88 and 9| closed the compressor in the refrigeration system will be operating to lower the pressure in the low pressure line of the system in a. manner well known in the art.

When the pressure in the system has fallen below the predetermined amount, the pin 38 will be retracted, enabling spring 48 to move beam 28 clockwise about its pivot |5 to the position shown in Fig. 2. This movement of beam 20 will, through the spacer 29, move actuating beam I6 clockwise about its pivot l5. This movement of beam IE will move the spring 60 above the plane of the lever 6|. The upward force then exerted by spring 60 on the lever 6| will snap lever 6| from its position in Fig. 1 to its position in Fig. 2. As the lever 6| nears its limit of upward motion, its free end will engage the ear 84, and move the switch arm 8| to open the contacts 88 and 9|. place against the force of spring 89. As arm 8| is moved into the position shown in Fig. 2, the member 61 will be rotated clockwise about its pivot l5 by the spring 18 and into latching engagement with the notched portion 86 of the member 85. Opening of contacts 88 and 9| breaks the circuit to the compressor motor, completing the cycle of operation.

It will be noted that, as lever 6| moves from its position in Fig. 1 toward its position in Fig. 2, the contacts 88 and BI are held closed positively by the force of spring 89 until the lever 6| strikes car 84 to open the contacts. At this point in its movement lever 8| will be moving at an accelerated rate and will move arm 8| to open contacts 88 and 9| abruptly. The mechanism controlling the switch contacts 88 and 9| does not, therefore, pass through a zone of vanishing contact pressure, but holds the contacts 88 and 9| positively closed until they are abruptly opened by the rapid movement of lever 6|. Likewise, upon actuation of the contacts to closed position, the member 67, by its latching engagement with member 85, will hold the contacts open until lever 6| strikes the lower portion of member 61 to remove it from engagement with member 85. Contacts 88 and 9| will thereupon be abruptly closed by the force of spring 89.

The cut-in point or the pressure value at which the contacts 88 and 9| will close may be adjusted by means of screw 42 to vary the force opposing motion of the pin 38. It will be noted that the adjustment of spring 46 has no efiect on the cutout point adjustment since beam 20, in moving to its position shown in Fig. 1, has left beam 25 behind and in engagement with the screw 54. The tension of spring 46, which may be adjusted by means of screw 50, does, however, determine the cut-out point or the pressure value at which the contacts 88 and 9| will open. As beam 20 moves from its position as shown in Fig. 1 to its position as shown in Fig. 2, at an intermediate point in its movement its free end engages the free end of beam 25 and moves it away from screw 54. During this latter portion of the move-- ment of beam 20 toward its position of Fig. 2,

This movement of arm 8| takes 0 In Fig. 3 is shown the positions assumed by the various parts of the mechanism when excessive pressure exists on the high side of the refrigeration system. Under these emergency conditions, contacts 88 and 9| have been opened although the pressure responsive assembly 36 and beam 28 are in their contact closing positions (Fig. 1). In response to the excessive pressure condition, pin 9'! has been extended by the pressure responsive assembly 94 to move beam l6 clockwise about its pivot l5 sufiiciently to actuate the switching mechanism to open-contact position. This movement of beam I6 takes place independently of the position of beam 20 and results in compression of spring 32.

it will be understood that other lever arrangemerits, having differing methods of adjustment, may be used to move lever 6| through its range of movement with a snap action and yet retain the features of the present invention which is to be limited only by the appended claims.

I claim:

1. In a control mechanism, a first pivotally movable lever carrying control means thereon, a movable member biased into latching engagement with said first lever by a resilient means, a second lever pivotally movable between first and second positions and engaging said first lever during movement toward said first position to permit id to move into latching engagement with said first lever, said second lever engaging said member during movement toward said second position to overcome said resilient means and remove said member from latching engagement with said first lever.

2. In a switch mechanism, a first pivotally movable lever having an electrical contact mounted thereon, a stationary electrical contact mounted for engagement with said first mentioned contact,

a movable member biased into latching engagement with said first lever by a resilient means, a second lever pivotally movable between first and second positions and engaging said first lever during movement toward said first position to ermit said member to move into latching engagement with said first lever, said second lever engaging said member during movement toward said second position to overcome said resilient means and remove said member from latching engagement with said first lever.

3. A circuit controlling device comprising a switch member movable between open and closed circuit positions, biasing means for holding said switch member in closed circuit position, a latch member movable to a latching position to retain said switch member in open circuit position against the force of said biasing means once said switch member has been moved to said open circuit position, a first operating lever, a second operating lever, resilient means connecting said operating levers and movable over center by said second operating lever whereby said first operating lever is moved between two limiting positions with a snap action, said first operating lever engaging said switch member during movement toward one of said limiting positions to move said switch member to open circuit position and thereby permit said latch member to move to said. latching position, said first operating lever engaging said latch member during movement toward the other of said limiting positions to move said latch member away from said latching position and thereby permit said biasing means to move said switch member to closed circuit position.

4. A circuit controlling device comprising a switch member movable between open and closed circuit positions and carrying a notched portion adjacent one of its ends, biasing means for holding said switch member in closed circuit position, a latch member biased to move into engagement with said notched portion to retain said switch member in open circuit position against the force of said biasing means once said switch member has been moved to said open circuit position, a first operating lever, a second operating lever, resilient means connecting said operating levers and movable over center by said second operating lever whereby said first operating lever is moved between two limiting positions with a snap action, said first operating lever engaging said switch member during movement toward one of said limiting positions to move said switch member to open circuit position and thereby permit said latch member to move into engagement with said notched portion, said first operating lever engaging said latch member during movement toward the other of said limiting positions to move said latch member out of engagement with said notched portion and thereby permit said biasing means to move said switch member to closed circuit position.

5. A controlling device comprising a control member movable between first and second controlling positions, biasing means for holding said control member in its said first controlling position, a latch member movable to a latching position to retain said control member in its said second controlling position once said control member has been moved to said second controlling position, means biasing said latch member into said latching position, a first operating lever, a second operating lever, resilient means connecting said operating levers and movable over center by said second operating lever whereby said first operating lever is moved between two limiting positions with a snap action, said first operating lever engaging said control member during movement toward one of said limiting positions to move said control member to its said second controlling position and thereby permit said latch member to move to said latching position, said first operating lever engaging latch member during movement toward the other of said limiting positions to move said latch member away from latching position and thereby permit said biasing means to move said control member to its said first controlling position. 4

6. In a switch mechanism, a first pivotally movable lever having an mounted for engagement with said first mentioned contact, an arc extinguishing magnet mounted adjacent said stationary contact, a movable member biased into latching engagement with said first lever, a second lever pivotally movable between first and second positions and engaging said first lever during movement toward said first position to permit said member to move into latching engagement with said first lever, said second lever engaging said member during movement toward said second position to remove said member from latching engagement with said first lever.

7. In a condition responsive controller, an actuating beam, control means actuated upon movement of said actuating beam, an actuated beam, said actuating beam being coextensive with said actuated beam and mounted for movement independent of said actuated beam, yieldelectrical contact mounted thereon, a stationary electrical contact able means exerting a force for holding said actuated and actuating beams in predetermined spaced relationship whereby they are moved in unison during normal operation of said controller, condition responsive means for moving said actuated beam upon a normal change in said condition, adjustable resilient means opposing movement of said actuated beam in one direction, a differential beam coextensive with said actuated and actuating beams and mounted for movement independent of said actuated and actuating beams, adjustable resilient means biasing said differential beam in said one direction, said differential beam being engaged and moved by said actuated beam upon movement thereof by said condition responsive means, a stop member limiting movement of said differential beam in said one direction and effective to cause disengagement of said actuated beam and said differential beam during final movement of said actuated beam in said one direction and during initial movement of said actuated beam in the other direction, and emergency condition responsive means for moving said actuating beam independently of said actuated beam and against the force exerted by said yieldable means.

8. In a pressure responsive controller having emergency shut-down means, an actuating beam, control means actuated upon movement of said actuating beam, a pivotally mounted actuated beam, said actuating beam being coextensive with said actuated beam and pivotally mounted for movement independent of said actuated beam, yieldable means exerting a force for holding said actuated and actuating beams in predetermined spaced relationship whereby they are pivotally moved in unison during normal operation of said controller, pressure responsive means for moving said actuated beam upon a normal change in said pressure, adjustable range spring means opposing movement of said actuated beam in one direction, a differential beam coextensive with said actuated and actuating beams and pivotally mounted for movement independent of said actuated and actuating beams, adjustable difierential spring means biasing said differential beam in said one direction, said differential beam being engaged and moved by said actuated beam upon movement thereof by said pressure responsive means, a stop member limiting movement of said differential beam in said one direction and effective to cause disengagement of said actuated beam and said differential beam during final movement of said actuated beam in said one direction and during initial movement of said actuated beam in the other direction, said emergency shut-down means comprising an emergency pressure responsive means for pivotally moving said actuating beam to actuate said control means independently of said actuated beam and against the force exerted by said yieldable means.

9. In a pressure responsive controller having emergency shut-down means, a pivotally mounted actuated beam, an actuating beam pivotally mounted intermediate its ends and having the portion on one side of said pivotal mounting coextensive with said actuated beam, switch actuating means secured to the portion of said actuating beam on the other side of said pivotal mounting, means including a strain-release spring exerting a force for holding said actuated and actuating beams in predetermined spaced relationship whereby they are pivotally moved in unison during normal operation of said controller, pressure responsive means for moving said actuated beam and consequently said actuating beam upon a normal change in pressure, adjustable range spring means opposing movement of said actuated beam in one direction, a pivotaliy mounted differential beam generally coextensive with said actuated beam and engageable thereby, adjustable differential spring means biasing said differential beam for pivotal movement in said one direction, an adjustable stop engageable by said diiierential beam for halting movement thereof in said one direction, whereby the force exerted by said diiferential spring means opposes the force exerted by said range spring means until said adjustable stop is engaged by said differential beam whereupon the unopposed force of said range spring is exerted against further movement of said actuated beam in said one direction, said emergency shut-down means comprising pressure responsive means responsive to abnormal pressure values and engageable with said actuating beam upon the occurrence of such abnormal pressure values for moving said actuating beam independently of said actuated beam against the force exerted by said strain relief spring.

10. In a pressure responsive controller having emergency shut-down means, a pivotally mounted actuated beam, an actuating beam pivotally mounted intermediate its ends and having the portion on one side of said pivotal mounting coextensive with said actuated beam, switch ac tuating means secured to the portion of said actuating beam on the other side of said pivotal mounting, means including a strain-release spring exerting a force for holding said actuated and actuating beams in predetermined spaced relationship whereby they are pivotally moved in unison during normal operation of said controller, pressure responsive means for moving said actuated beam and consequently said actuating beam upon a normal change in pressure, adjustable range spring means opposing movement of said actuated beam in one direction, a pivotally mounted differential beam generally coextensive with said actuated beam and engageable thereby, adjustable differential spring means biasing said differential beam for pivotal movement in said one direction, an adjustable stop engageable by said differential beam for halting movement thereof in said one direction, whereby the force exerted by said differential spring means opposes the force exerted by said range spring means until said adjustable stop is engaged by said differential beam whereupon the unopposed force of said range spring is exerted aga 1st further movement of said actuated beam in said one direction, said emergency shut-down means comprising pressure responsive means responsive to abnormal pressure values and engageable with said actuating beam at said other side of said pivotal mounting upon the occurrence of such abnormal pressure values for moving said actuating beam independently of said actuated beam against the force exerted by said strain relief spring.

LLOYD R. EIMERMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 806,325 Crawford et a1 Dec. 5, 1905 1,728,242 Lobley Sept. 17, 1929 1,966,106 Shivers July 10, 1934 2,280,262 Purat Apr. 21, 1942 2,418,965 Blair Apr. 15, 1947 FOREIGN PATENTS Number Country Date 463,694 Germany Sept. 19, 1924 

